1. Field of the Invention
The present invention relates to a pack case for a secondary battery. More particularly, the present invention relates to a pack case with an improved arrangement for accommodating a secondary battery therein.
2. Description of the Prior Art
Recently, electronic appliances having compact sizes and light weight, such as cellular phones, notebook computers and camcorders, have been actively developed and produced. Such electronic appliances are equipped with battery packs so that users can use the electronic appliances in various places even if electric power sources are not separately provided for the electronic appliances. The battery pack includes at least one battery capable of outputting an operational voltage having a predetermined level in order to operate the electronic appliances for a predetermined period of time.
Secondary batteries, which are rechargeable batteries, are currently employed in the secondary pack due to their economical advantages. Secondary batteries include Ni—Cd batteries, Ni—MH batteries and Li secondary batteries, such as Li batteries or Li-ion batteries.
In such secondary batteries, most unit cells include an electrode assembly having a positive electrode, a negative electrode and a separator interposed between the positive electrode and the negative electrode. The electrode assembly is accommodated in a can made from aluminum or an aluminum alloy and the can is sealed by means of a cap assembly. After the can has been sealed by the cap assembly, an electrolyte is injected into the can through an electrolyte injection hole, and then the electrolyte injection hole is sealed, thereby completing the fabrication of the secondary battery. Although iron may be used as a material for the can, if the can is fabricated by using aluminum or an aluminum alloy, the secondary battery has a light weight while being resistant to erosion even if the secondary battery is used for a long period of time under high voltage.
The battery pack is constructed using a plurality of unit cells. In general, the battery pack includes a pack case having an insulation property. In addition, a plurality of batteries, wiring circuits for electrically connecting the batteries to each other, safety devices and contact terminals are accommodated in the pack case for the secondary battery.
For example, a sealed unit cell connected with battery accessories and safety devices, such as a positive temperature coefficient (PTC) device, a thermal fuse and a protective circuit module (PCM), may be accommodated in the battery pack. Alternatively, in a state in which the unit cell connects to the PCM and battery accessories, molding resin is filled in gaps formed between the above elements in such a manner that the unit cell, the PCM and battery accessories may be clad or fixed together, thereby forming the battery pack.
The safety devices are connected to positive and negative electrode terminals of the unit cell through a predetermined conductor structure called a “lead” in order to prevent the secondary battery from malfunctioning by the interruption of current applied to the secondary battery when, for instance, the voltage of the secondary battery suddenly rises due to the high temperature in the secondary battery or over-charge/over-discharge of the secondary battery.
However, a conventional pack case for the secondary battery is not available if the number of secondary batteries mounted in the pack case is reduced or increased.
Therefore, a separate pack case adaptable for only one battery must be provided when it is necessary to mount only one secondary battery in the pack case adaptable for two secondary batteries.
In addition, since the size of the pack cases is generally standardized, if only one secondary battery is mounted in the pack case adaptable for mounting two secondary batteries, the secondary battery may not be fixedly mounted in the pack case, so that the secondary battery may not stably connect with the PCM or other battery accessories.